Set Site Header Height

First of all, thank you for this wonderful theme.

I was wondering about the site header height. We can set it in the theme option but as the value goes up it create a larger gap between the logo and the upper end. I was hoping to make the header longer at the bottom and like the live demo of the free theme. When I compare my web and the live demo the site header is longer and does not create a huge gap between the logo/menu and the topbar.

I am using the 1.2.8